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  • Title: Properties of an endonuclease activity in Micrococcus luteus acting on gamma-irradiated DNA and on apurinic DNA.
    Author: Schäfer G, Haas P, Coquerelle T, Hagen U.
    Journal: Int J Radiat Biol Relat Stud Phys Chem Med; 1980 Jan; 37(1):11-18. PubMed ID: 6245038.
    Abstract:
    A protein fraction from Micrococcus luteus with endonuclease activity against gamma-irradiated DNA was isolated and characterized. An additional activity on apurinic sites could not be separated, either by sucrose gradient sedimentation or by gel filtration through Sephadex G 100. From gel filtration, a molecular weight of about 25 000 was calculated for both endonuclease activities. The endonuclease activity against gamma-irradiated DNA was stimulated five-fold with 5 mM Mg++, whereas that against apurinic sites was less dependent on the Mg++ concentration. 100 mM KCl inhibited the gamma-ray endonuclease, but not the apurinic endonuclease activity. In gamma-irradiated RNA the protein recognized 1.65 endonuclease sensitive sites per radiation induced single-strand break, among which are 0.45 alkali labile lesions in the nucleotide strand. The affinity of the enzyme for the endonuclease sensitive site was evaluated resulting in a Km-value of 73 nM.
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